In the area of a sports arena which is a closed building of large size for sports events such as hockey, curling, basketball and indoor soccer, there is a great need for acoustic management in that noise reverberation comes from the walls and ceiling of the building, sometimes with 1-10 second delays.
At the same time, for musical performance and political or religious inspirational talks, there is a similar need for acoustical management so that echoes 1-10 or more seconds later will not mar the performance or dampen the charisma of the speaker. They are dampened to 0.5 to 2.0 seconds.
While there is need for acoustical treatment, the roar of the crowd and its reverberation is an exciting feature of a sporting event. Therefore, there are times when long reverberation is acceptable and other times when it is desirable to dampen it. Sometimes there is a thermal problem for an arena, as in a hockey game or basketball, particularly when the arena is in an air conditioning mode. The arena may have on the ground floor a temperature of 60+ degrees F and a ceiling temperature of 100 degrees F at 150 feet in the air. Ceiling temperatures generally range from 95.degree. F. to 115.degree. F. because heat rises. From the ceiling, the reradiation of emissivity, as distinct from convection heat transfer, will heat the floor to undesirable levels. Thus, the emissivity from a black ceiling would be 98%, and from a white ceiling would be 90%. From a silver or aluminum ceiling, the emissivity Ec will be only 3%. With hockey, the ice would be 25.degree. F. to 30.degree. F. and refrigeration load is then very high if the emissivity is not controlled.